Fish that you plan to keep and eat later, need to be kept fresh to prevent the meat from making you ill.
To assure that it is fresh, keep it alive until it is cleaned, which prevents any danger of spoilage.

Place your fish into a live well, or on a stringer in the water, or failing that, in a cooler filled with stream water.

Cleaning a fish

Cleaning your catch tends to be a little messy, but isn’t at all difficult.
Place the knife tip into the fish’s vent and move the blade up along the belly, cutting to the head. Keep the knife placement shallow so you don’t puncture the entrails.
Spread open the body and remove the intestines, and scrape the backbone.
Cut the head off, and rinse the fish in some clean water.

Once you have it cleaned, it needs to be put on ice or in a cooler.
Don’t store your fish in ice water, but permit the water to drain from the cooler as it melts.

Scaling

While some fish don’t have scales many more do and they need to be removed from the fishes skin. Lay the fish on a flat surface, holding it by the head with one hand.
Lay your knife rather sideways against the fish and rake it from the tail toward the head.
Make sure that you scale both sides of the fish.
Bluegill and crappie are usually scaled first, then cleaned and most of the time cooked while they are whole.
Remove the bones of course before you eat the fish.

Skinning

Removing the skin improves the taste of a lot of fish. It also removes a layer of fat just under the skin. Catfish are usually skinned because their skin is so tough and is not at all palatable.

To skin a catfish or bullhead, hold its head firmly on a flat surface with a clamp.
I like to snip off a catfish’s spines before skinning them because they can give a nasty spike to a hand.
Cut through the skin that is behind the head, and pull down with pliers.

Filleting

means getting the meat of the fish without the bones. Larger fish like bass, pike, salmon, and walleye, are very often filleted. A filleted fish has its skin and all of its bones removed before cooking. Scaling isn’t necessary. Fillet knives have a long, thin, blade that’s very sharp and made specifically for this purpose.

For Filleting Fish

Lay the fish on its side on a flat surface.
Cut the fish behind its gills and pectoral fin down to, but not through, the backbone. Without removing the knife, turn the blade and cut through the ribs toward the tail. Use the fish’s backbone to guide you. Turn the fish over and repeat the steps.